1. Field of the Invention
The present invention relates generally to a fluid control technique, and more particularly to a Venturi tube assembly and a manual/pneumatic pump including the Venturi tube assembly.
2. Description of the Related Art
In the field of vehicle service technique, a Venturi tube is often applied to a service tool as a component thereof for lowering air pressure in a closed space. FIG. 1 shows a conventional Venturi tube assembly 90 having an inlet end 901 and an internal flow passage 902 with different diameters of sections. After high-pressure gas enters the inlet end 901 of the Venturi tube assembly 90, the high-pressure gas flows through the different diameters of sections of the internal flow passage 902 at different speeds to create different pressure environments in different positions. Accordingly, the gas in an external closed space 91 in communication with a low static pressure section 903 of the flow passage 902 can be sucked into the flow passage 902 to gradually lower the pressure in the space 91.
In a vehicle service site, an air compressor is often practically used as a high-pressure gas source for the Venturi tube assembly 90 to suck out fuel of a vehicle.
Please further refer to FIG. 2. In the conventional technique, the Venturi tube assembly 92 can be used in another mode for increasing pressure in a closed space. A movable blocking member 922 is disposed at the outlet end 921 of the Venturi tube assembly 92. When the blocking member 922 is positioned in a blocking position to block the outlet end 921, the high-pressure gas entering the Venturi tube assembly 92 will reversely flow from the low static pressure section 923 into the closed space 93 to increase air pressure in the closed space 93. Under such circumstance, the fuel originally contained in the space 93 will be driven to flow out of the space 93 so as to vacate the space 93 for next fuel sucking operation.
According to the above arrangement, the direction in which the gas flows within the Venturi tube assembly can be changed to achieve both sucking and exhaustion effects. However, in the exhaustion operation, a mass of high-pressure gas will very quickly flows from the Venturi tube assembly into the closed space. In case the strength of the container defining the closed space is insufficient, the container may explode to put the operator in danger.